Reversed-phase Dispersive Liquid-liquid Microextraction Research Articles

Deep Eutectic Solvent Based Reversed-Phase Dispersive Liquid-Liquid Microextraction and High-Performance Liquid Chromatography for the Determination of Free Tryptophan in Cold-Pressed Oils.

A fast and straightforward reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) using a deep eutectic solvent (DES) procedure to determine free tryptophan in vegetable oils was developed. The influence of eight variables affecting the RP-DLLME efficiency has been studied by a multivariate approach. A Plackett-Burman design for screening the most influential variables followed by a central composite response surface methodology led to an optimum RP-DLLME setup for a 1 g oil sample: 9 mL hexane as the diluting solvent, vortex extraction with 0.45 mL of DES (choline chloride-urea) at 40 °C, without addition of salt, and centrifugation at 6000 rpm for 4.0 min. The reconstituted extract was directly injected into a high-performance liquid chromatography (HPLC) system working in the diode array mode. At the studied concentration levels, the obtained method detection limits (MDL) was 11 mg/kg, linearity in matrix-matched standards was R2 ≥ 0.997, relative standard deviations (RSD) was 7.8%, and average recovery was 93%. The combined use of the recently developed DES -based RP-DLLME and HPLC provides an innovative, efficient, cost-effective, and more sustainable method for the extraction and quantification of free tryptophan in oily food matrices. The method was employed to analyze cold-pressed oils from nine vegetables (Brazil nut, almond, cashew, hazelnut, peanut, pumpkin, sesame, sunflower, and walnut) for the first time. The results showed that free tryptophan was present in the range of 11-38 mg/100 g. This article is important for its contributions to the field of food analysis, and for its development of a new and efficient method for the determination of free tryptophan in complex matrices, which has the potential to be applied to other analytes and sample types.

Trace determination of prohibited acrylamide in cosmetic products by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and liquid chromatography-tandem mass spectrometry

An analytical method for the determination of residual acrylamide in cosmetic products containing potential acrylamide-releasing ingredients is presented. The method is based on vortex-assisted reversed-phase dispersive liquid-liquid microextraction (VA-RP-DLLME) to extract and preconcentrate acrylamide by using water as extraction solvent taking advantage the highly polar behavior of this analyte, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) for its determination. Under optimized conditions (5 mL toluene as supporting solvent, 50 µL of water as extraction solvent, 1 min for vortex extraction time) the method was properly validated obtaining good analytical features (linearity up to 20 ng mL−1, method limits of detection and quantification of 0.51 and 1.69 ng g−1, respectively, enrichment factor of 52, and good repeatability (RSD < 4.1%)). The proposed analytical method was applied to the determination of acrylamide in commercial samples that were weighed and dispersed in the minimum quantity of methanol (50 µL) by vortex stirring before applying the VA-RP-DLLME procedure. Through the pretreatment of the sample and the use of acrylamide-d3 as surrogate, the matrix effect was overcome, obtaining good relative recovery values (88–108%). The proposed method has shown efficacy, simplicity, and speed, and it allows the determination of acrylamide at trace levels easily, which could make it very useful for companies in the quality control of cosmetic products containing potential acrylamide-releasing ingredients to fulfill the safety limits imposed by European Regulation.

Vitamin E determination in edible oils by reversed-phase dispersive liquid-liquid microextraction and screen-printed carbon electrodes

• Rapid, simple and environmentally friendly determination of vitamin E in edible oils. • Reversed-phase dispersive liquid-liquid microextraction as ecological sample preparation. • Inexpensive and commercially available screen-printed electrodes for detection. • Analytical Eco-Scale for assessing the greenness of the method. A novel simple, environmentally friendly and portable method to determine vitamin E in edible oils based on reversed-phase dispersive liquid-liquid microextraction combined with electrochemical detection using screen-printed carbon electrodes (SPCEs) has been developed. Vitamin E was extracted from oil samples into a 4 M HCl aqueous solution and determined by differential pulse voltammetry using SPCEs. The extraction conditions optimized by experimental design (i.e., Plackett–Burman and central composite designs) were: aqueous 4 M HCl extractant volume, 43 µL; extraction time, 2 min; centrifugation time, 10 min; and centrifugation speed, 3000 rpm. The proposed method requires a standard addition calibration approach, and the working range showed good linearity from 0 to 20 mg L −1 , with a correlation coefficient ranging from 0.990 to 0.995 ( N =5). The methodological limit of detection was between 1 and 3 mg L −1 . The repeatability of the proposed method was evaluated at 15 mg L −1 , and the relative standard deviation ranged between 10 and 15% ( n =5). For the quantification of vitamin E in ten commercial samples of olive, sesame, soybean, sunflower and a mixture of sunflower and corn oils, the volume of the extractant phase (i.e., 4 M HCl aqueous solution) was increased up to 100 µL and satisfactory recoveries were obtained in the range of 85–115%, confirming the applicability of the method.

Reversed-phase dispersive liquid-liquid microextraction based on decomposition of deep eutectic solvent for the determination of lead and cadmium in vegetable oil

In this work, a reversed-phase dispersive liquid-liquid microextraction procedure based on the decomposition of deep eutectic solvent was suggested for the first time. The procedure was utilized for fast and simple separation of lead and cadmium from vegetable oil samples. The procedure assumed mixing of oil sample and DES based on menthol, formic acid and water. Water as component of DES promoted its decomposition in sample matrix resulting menthol dissolution in the sample phase and dispersion of aqueous formic acid solution. In this procedure menthol acted as a dispersive solvent during DES decomposition for dispersion of aqueous formic acid solution. The metals were determined by the square-wave anodic stripping voltammetry. The limits of detection, were 0.01 µg kg−1 for lead and 0.006 µg kg−1 for cadmium. The RSD was less then 6% for both analytes. The enrichment factor was 36 and 39 for lead and cadmium, respectively.

Microwave absorption medium-assisted extraction coupled with reversed-phase dispersive liquid-liquid microextraction of triazine herbicides in corn and soybean samples.

A new extraction method, microwave absorption medium-assisted extraction coupled with reversed-phase dispersive liquid-liquid microextraction, was developed for the determination of triazine herbicides in corn and soybean samples. Triazine herbicides were extracted with hexane and then directly enriched into the ionic liquid phase. The purification of sample and concentration of target analytes were performed simultaneously. The method combines the advantages of nonpolar solvent dynamic microwave extraction and reversed-phase dispersive liquid-liquid microextraction, which could greatly simplify the operation and reduce the whole pretreatment time. The Box-Behnken design was used to the optimization of experimental factors involved in the dynamic microwave-assisted extraction. In the present study, good linearity in the range of 5.00-500.00µg/kg was obtained. The limits of detection and quantification varying from 1.3 to 4.2 and 4.1 to 13.9µg/kg were achieved, respectively. The intra- and interday precisions were between 2.7 and 6.9%. The present method was applied to the analysis of corn and soybean samples, and the recoveries of analytes ranged from 80.7 to 106.9% with the relative standard deviations of 2.1-7.8%. The present method shows the potentials of practical applications in the treatment of the complex fatty solid samples.

Application of deep eutectic solvent as a disperser in reversed-phase dispersive liquid-liquid microextraction for the extraction of Cd(II) and Zn(II) ions from oil samples

A new, sensitive, and safe pretreatment method for the analysis of Cd(II) and Zn(II) ions in oil samples prior to flame atomic absorption spectrometry was developed. For the first time, a deep eutectic solvent is used as a disperser in reversed-phase dispersive liquid-liquid microextraction procedure. For this purpose, a deep eutectic solvent with low viscosity and miscible with both aqueous and organic phases is prepared by mixing glycolic acid and mandelic acid at a molar ratio of 2:1. The variables involved in this process were studied to provide high enrichment factors. Under optimized conditions, the linear ranges of calibration curves for Cd(II) and Zn(II) ions were obtained 0.30−20 and 0.50−30 μg L−1, respectively. The obtained detection limits and enrichment factors were 0.12 and 0.18 μg L−1; and 32.7 and 32.2 for Cd(II) and Zn(II), respectively. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 2.7 to 4.1 % (n = 6, C = 1 μg L−1 of each cation). Finally, the proposed method was successfully applied for the determination of Cd(II) and Zn(II) concentrations in various oil samples.

A new and feasible analytical method using reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for further determination of Nickel in hydrogenated vegetable fat

A new and simple method for Ni determination in hydrogenated vegetable fat (HVF) has been developed using a RP-DLLME sample preparation procedure for further determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrophotometry (GFAAS). The RP-DLLME procedure includes simultaneous microextraction and preconcentration of Ni in HVF, using 5.0 g of HVF preheated (75 °C) and diluted in 5.0 mL of xylene, with the addition of a dispersant/extractant mixture (n-propanol/dilute HNO3). The sample was manually stirred and centrifuged and the aqueous phase was collected for further Ni determination by FAAS and GFAAS. RP-DLLME was carried out using only 700 μL of n-propanol and 300 μL of 2.0 mol L−1 HNO3. The recovery varied from 93.3% to 101.5% for HVF. The LODs and LOQs were 40 and 90 ng g−1 for FAAS, and 0.41 and 1.36 ng g−1 for GFAAS. The proposed analytical method is viable and this is the first application of RP-DLLME to solid fat samples, with Ni determination as an example of application. This method consumes small amounts of reagents, with lower toxicity as compared to microwave decomposition. Furthermore, the key features of the RP-DLLME method include simplicity of operation, high sample mass, reduced reagent consumption, and use of diluted HNO3 as an extractant.

Reversed-Phase Dispersive Liquid-Liquid Microextraction (RP-DLLME) as a Green Sample Preparation Method for Multielement Determination in Fish Oil by ICP-OES

A new and simple method for Cd, Fe, Mn, Ni, Pb, and Zn determination in fish oil by inductively coupled plasma optical emission spectrometry (ICP-OES) was developed using reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for sample preparation. The RP-DLLME method was based on the simultaneous extraction and pre-concentration of analytes in fish oil, using 10.0 g of sample preheated (75 °C), with the addition of a dispersant/extractant mixture (n-propanol/diluted HNO3 solution). After stirring and centrifugation (5600g, 10 min), the aqueous phase was used for analyte determination. The RP-DLLME method was performed using only 700 μL of n-propanol and 300 μL of 2.0 mol L−1 HNO3 solution. The recoveries for Cd, Mn, Ni, and Zn using the spikes of 100 and 500 μg kg−1 ranged from 86.4 to 93.4% and 90.4 to 97.3%, respectively. For Fe and Pb, the recoveries ranged from 85.7 and 90.0% and 85.3 and 94.4% for the same spikes. The limits of quantification (LOQs) were 0.41, 1.98, 0.33, 0.35, 1.52, and 1.39 μg kg−1 for Cd, Fe, Mn, Ni, Pb, and Zn, respectively. The proposed RP-DLLME sample preparation method allowed analyte extraction for further determination by ICP-OES using a small amount of diluted HNO3 solution avoiding applying a sample decomposition step. The extract was suitable for direct introduction in the ICP-OES equipment and reached LOQs values lower than similar methods from literature. Finally, the proposed analytical method was viable and this is the first application of RP-DLLME for animal source fat combined with ICP-OES determination.

Ultrasound-Assisted Matrix Solid-Phase Dispersion Coupled with Reversed-Phase Dispersive Liquid–Liquid Microextraction for Determination of Vitamin C in Various Matrices

For the first time, ultrasound-assisted matrix solid-phase dispersion (UA-MSPD) and reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) were coupled for determination of vitamin C in various matrices without any filtration and sample transfer from the original vessel. Samples were analyzed using a high-performance liquid chromatography (HPLC) instrument with ultraviolet absorption detector. Influential parameters of UA-MSPD and RP-DLLME such as sorbent, elution solvent and its volume, sample to sorbent ratio, ultrasonic time and amplitude, pH of aqueous phase and its volume, water-immiscible organic solvent and its volume, and centrifuging time were investigated and optimized. Under the optimized conditions, limit of detection and quantitation values were 0.84 and 2.5 ng/mL, respectively. Recovery data for several real samples were obtained in the range of 67.0–88.0% with relative standard deviation (RSD) less than 7.5%. The proposed method was successfully applied to quantitatively determination of vitamin C in several solid and semi-solid samples.

A simple, rapid and low cost reversed-phase dispersive liquid-liquid microextraction for the determination of Na, K, Ca and Mg in biodiesel

In this work a method based on reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) as sample preparation for the extraction and preconcentration of Na, K, Ca and Mg in biodiesel samples was developed. The analytes determination was performed by flame atomic absorption spectrometry (FAAS), operating in emission mode for Na and K and in absorption mode for Ca and Mg. The extraction/preconcentration step of the analytes was performed by using a mixture of dispersant and extractant solvents (isopropanol and HNO3, respectively) and the aqueous phase containing the analytes was separated by centrifugation. Some parameters such as sample mass, type and volume of dispersant and extractant solutions, HNO3 concentration (extraction solution), use of ultrasound, centrifugation time and temperature were evaluated. During the optimization of RP-DLLME, biodiesel samples were spiked with a multi-element biodiesel B100 (Conostan®) with final concentration of 1.0 μg g−1 of the analytes. Analytes determination was performed by FAAS using external calibration with aqueous reference solutions. The limits of quantification (LOQ) for Na, K, Ca and Mg were 0.04; 0.02; 0.05 and 0.08 µg kg respectively. The accuracy was evaluated by recovery tests, which ranged from 93.9% to 108.1%, with relative standard deviation lower than 3% for all analytes. Then, the proposed method was applied for analytes determination in five biodiesel samples produced from different raw materials. Comparing to conventional methods for elements determination in biodiesel (e.g., dilution with organic solvent, sample digestion, etc.), RP-DLLME combined to FAAS is simple, low cost, low reagents consumption and provides LOQs values significantly below compared to the limits established in the legislation for these elements in biodiesel.

Salt-assisted liquid–liquid extraction coupled with reversed-phase dispersive liquid–liquid microextraction for sensitive HPLC determination of paraquat in environmental and food samples

In this study, salt-assisted liquid–liquid extraction (SALLE) method is coupled with reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) as a novel method for the determination of paraquat in various samples. Firstly, paraquat was extracted from the aqueous phase into the acetonitrile and then it pre-concentrated into the aqueous phase using the RP-DLLME method. Influential parameters of SALLE such as extracting solvent, volume of extracting solvent, sample pH, salt and its concentration were optimized. Also, effective parameters of RP-DLLME including immiscible solvent and its volume, and water volume as extracting solvent were investigated. Under the optimized conditions recoveries and relative standard deviations were in the range of 80.0–96.0 and 3.5–7.5, respectively. The limit of detection and limit of quantification of method were 0.02 and 0.09 µg/mL, respectively. The proposed method successfully was applied for the determination of paraquat in food and environmental samples.

Determination of N-nitrosamines in cosmetic products by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and liquid chromatography with mass spectrometry.

A new analytical method for the simultaneous determination of trace levels of seven prohibited N-nitrosamines (N-nitrosodimethylamine, N-nitrosoethylmethylamine, N-nitrosopyrrolidine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosomorpholine, and N-nitrosodiethanolamine) in cosmetic products has been developed. The method is based on vortex-assisted reversed-phase dispersive liquid-liquid microextraction, which allows the extraction of highly polar compounds, followed by liquid chromatography with mass spectrometry. The variables involved in the extraction process were studied to obtain the highest enrichment factor. Under the selected conditions, 75μL of water as extraction solvent was added to 5mL of n-hexane sample solution and assisted by vortex mixing during 30s to form the cloudy solution. The method was successfully validated showing good linearity (0.5-50ng/mL), enrichment factors up to 65 depending on the target compound, limits of detection values of 1.8-50ng/g, and good repeatability (RSD<9.8%). Finally, the proposed method was applied to different cosmetic samples. Quantitative relative recovery values (80-113%) were obtained, thus showing that matrix effects were negligible. The achieved analytical features of the proposed method, besides of its simplicity and affordability, make it useful to perform the quality control of cosmetic products to ensure the safety of consumers.

Determination of free formaldehyde in cosmetics containing formaldehyde-releasing preservatives by reversed-phase dispersive liquid–liquid microextraction and liquid chromatography with post-column derivatization

An analytical method for the determination of traces of formaldehyde in cosmetic products containing formaldehyde-releasing preservatives has been developed. The method is based on reversed-phase dispersive liquid–liquid microextraction (RP-DLLME), that allows the extraction of highly polar compounds, followed by liquid chromatography–ultraviolet/visible (LC–UV/vis) determination with post-column derivatization. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the selected conditions, a mixture of 500 μL of acetonitrile (disperser solvent) and 50 μL of water (extraction solvent) was rapidly injected into 5 mL of toluene sample solution. The extracts were injected into the LC–UV/vis system using phosphate buffer 6 mmol L−1 at pH 2 as mobile phase. After chromatographic separation, the eluate merged with a flow stream of pentane-2,4-dione in ammonium acetate solution as derivatizing reagent and passed throughout a post-column reactor at 85 °C in order to derivatize formaldehyde into 3,5-diacetyl-1,4-dihydrolutidine, according to Hantzsch reaction, which was finally measured spectrophotometrically at 407 nm. The method was successfully validated showing good linearity, an enrichment factor of 86 ± 2, limits of detection and quantification of 0.7 and 2.3 ng mL−1, respectively, and good repeatability (RSD < 9.2%). Finally, the proposed analytical method was applied to the determination of formaldehyde in different commercial cosmetic samples containing formaldehyde-releasing preservatives, such as bronopol, diazolidinyl urea, imidazolidinyl urea, and DMDM hydantoin, with good relative recovery values (91–113%) thus showing that matrix effects were negligible. The good analytical features of the proposed method besides of its simplicity and affordability, make it useful to carry out the quality control of cosmetic products containing formaldehyde-releasing preservatives.

Rapid determination of hydrophilic phenols in olive oil by vortex-assisted reversed-phase dispersive liquid-liquid microextraction and screen-printed carbon electrodes

A novel approach is presented to determine hydrophilic phenols in olive oil samples, employing vortex-assisted reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for sample preparation and screen-printed carbon electrodes for voltammetric analysis. The oxidation of oleuropein, hydroxytyrosol, caffeic acid, ferulic acid and tyrosol was investigated, being caffeic acid and tyrosol selected for quantification. A matrix-matching calibration using sunflower oil as analyte-free sample diluted with hexane was employed to compensate matrix effects. Samples were analyzed under optimized RP-DLLME conditions, i.e., extractant phase, 1M HCl; extractant volume, 100µL; extraction time, 2min; centrifugation time, 10min; centrifugation speed, 4000rpm. The working range showed a good linearity between 0.075 and 2.5mgL−1 (r = 0.998, N = 7) for caffeic acid, and between 0.075 and 3mgL−1 (r = 0.999, N = 8) for tyrosol. The methodological limit of detection was empirically established at 0.022mgL−1 for both analytes, which is significantly lower than average contents found in olive oil samples. The repeatability was evaluated at two different spiking levels (i.e., 0.5mgL−1 and 2mgL−1) and coefficients of variation ranged from 8% to 11% (n = 5). The applicability of the proposed method was tested in olive oil samples of different quality (i.e., refined olive oil, virgin olive oil and extra virgin olive oil). Relative recoveries varied between 83% and 108% showing negligible matrix effects. Finally, fifteen samples were analyzed by the proposed method and a high correlation with the traditional Folin-Ciocalteu spectrophotometric method was obtained. Thereafter, the concentrations of the fifteen oil samples were employed as input variables in linear discriminant analysis in order to distinguish between olive oils of different quality.

Solid-phase extraction assisted dispersive liquid-liquid microextraction based on solidification of floating organic droplet to determine sildenafil and its analogues in dietary supplements.

A novel analytical method for the simultaneous determination of the concentration of sildenafil and its five analogues in dietary supplements using solid-phase extraction assisted reversed-phase dispersive liquid-liquid microextraction based on solidification of floating organic droplet combined with ion-pairing liquid chromatography with an ultraviolet detector was developed. Parameters that affect extraction efficiency were systematically investigated, including the type of solid-phase extraction cartridge, pH of the extraction environment, and the type and volume of extraction and dispersive solvent. The method linearity was in the range of 5.0-100ng/mL for sildenafil, homosildenafil, udenafil, benzylsildenafil, and thiosildenafil and 10-100ng/mL for acetildenafil. The coefficients of determination were ≥0.996 for all regression curves. The sensitivity values expressed as limit of detection were between 2.5 and 7.5ng/mL. Furthermore, intraday and interday precisions expressed as relative standard deviations were less than 5.7 and 9.9%, respectively. The proposed method was successfully applied to the analysis of sildenafil and its five analogues in complex dietary supplements.

Determination of N-nitrosodiethanolamine in cosmetic products by reversed-phase dispersive liquid-liquid microextraction followed by liquid chromatography

A new analytical method for the determination of N-nitrosodiethanolamine (NDELA), a very harmful compound not allowed in cosmetic products, is presented. The method is based on a new approach of dispersive liquid–liquid microextraction (DLLME) useful for extraction of highly polar compounds, called reversed-phase DLLME (RP-DLLME), followed by liquid chromatography–ultraviolet/visible (LC-UV/Vis) determination. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the optimized conditions, a mixture of 750µL of acetone (disperser solvent) and 125µL of water (extraction solvent) was rapidly injected into 5mL of toluene sample solution. The extracts were injected into the LC-UV/Vis system using ammonium acetate 0.02M as mobile phase. After chromatographic separation, the eluate passed throughout a photolysis unit in order to convert NDELA to nitrite, and then it was merged with a flow stream of Griess Reagent and passed throughout a post-column reactor at 50°C to derivatize nitrite into an azo-dye, which was finally measured spectrophotometrically at 540nm. The method was successfully validated showing good linearity, an enrichment factor of 31.5±0.9, limits of detection and quantification of 1.1 and 3.6ngmL−1, respectively, and a good repeatability (RSD <8%). Finally, the proposed analytical method was applied to the determination of NDELA in commercial cosmetic samples of different nature, specifically three lipophilic creams and a hydrophilic shower gel, with good relative recovery values (87 – 117%) thus showing that matrix effects are negligible. These results were compared with those obtained by applying the ISO 10130 official method, which uses the same detection approach. It was concluded that a great improvement in the sensitivity was achieved, whereas the use of organochlorine solvents is avoided and therefore it can be considered as a greener approach.

Development of coupled ultrasound-assisted and reversed-phase dispersive liquid-liquid microextraction before high-performance liquid chromatography for the sensitive determination of vitamin A and vitamin E in oil samples.

A new approach based on the ultrasound-assisted reversed-phase dispersive liquid-liquid microextraction technique is developed for the extraction and determination of vitamin A and vitamin E from oil matrices before high-performance liquid chromatography analysis. A methodology based on the full factorial design is carried out to choose the significant parameters. Then the significant factors affecting the extraction efficiency including pH, volume of extraction solvent, and volume of disperser solvent are optimized using a Box-Behnken design. After analyzing the results obtained, the optimum conditions were: pH 4.5, 80-20 μL of the ethanol/water solvent mixture as extraction solvent, 110 μL of 1,4-dioxane as the disperser solvent, and a sonication time of 10 min. For validation of the developed method, the linear dynamic range, repeatability, limit of detection, and recoveries were obtained under the optimum conditions. The detection limits of the method were 1.6 and 2.3 ng/mL for vitamin A and vitamin E, respectively. The extraction recovery percentages for the studied drugs were above 91%, with acceptable relative standard deviation. The proposed methodology was successfully applied for the determination of the vitamins in different oil samples.

Reversed-phase vortex-assisted liquid-liquid microextraction: a new sample preparation method for the determination of amygdalin in oil and kernel samples.

A novel, simple, and rapid reversed-phase vortex-assisted liquid-liquid microextraction coupled with high-performance liquid chromatography has been introduced for the extraction, clean-up, and preconcentration of amygdalin in oil and kernel samples. In this technique, deionized water was used as the extracting solvent. Unlike the reversed-phase dispersive liquid-liquid microextraction, dispersive solvent was eliminated in the proposed method. Various parameters that affected the extraction efficiency, such as extracting solvent volume and its pH, vortex, and centrifuging times were evaluated and optimized. The calibration curve shows good linearity (r(2) = 0.9955) and precision (RSD < 5.2%) in the range of 0.07-20 μg/mL. The limit of detection and limit of quantitation were 0.02 and 0.07 μg/mL, respectively. The recoveries were in the range of 96.0-102.0% with relative standard deviation values ranging from 4.0 to 5.1%. Unlike the conventional extraction methods for plant extracts, no evaporative and re-solubilizing operations were needed in the proposed technique.

Monitoring oxidative stability and phenolic compounds composition of myrtle-enriched extra virgin olive during heating treatment by flame, oven and microwave using reversed phase dispersive liquid–liquid microextraction (RP-DLLME)-HPLC-DAD-FLD method

Lipids oxidation is one of the main ways that affect the nutritional quality of extra virgin olive oil (EVOO) by losing its phenolic substances and especially during heating treatments. This study was focused on the evaluation of the effect of Myrtus communis phenolic compounds-enriched extra virgin olive oil (McPC-EEVOO) on phenolic compounds composition during flame, oven at 180°C and microwave heating, at different exposure times, evaluated by reversed phase dispersive liquid–liquid microextraction (RP-DLLME)-HPLC-DAD-FLD. The K232 and K270 were also evaluated for all heating treatments. The obtained results showed that the enrichment of EVOO by myrtle extracts significantly prevents the consumption of endogenous phenolic compound from EVOO as phenolic alcohol and flavonoids in comparison to the control (EVOO without enrichment). The most protective effect was found during flame and microwave heating. The K232 values were significantly reduced during flame heating compared to the control and followed by oven heating, although K232 values in microwave heating were similar for all the oil examines. K270 was not affected by this enrichment of EVOO.

New reversed phase dispersive liquid–liquid microextraction method for the determination of phenolic compounds in virgin olive oil by rapid resolution liquid chromathography with ultraviolet–visible and mass spectrometry detection

The determination of phenolic compounds in virgin olive oil using a new reversed phase dispersive liquid–liquid microextraction (RP-DLLME) procedure coupled with rapid resolution liquid chromatography-diode array and mass spectrometry detection (RRLC-DAD–MS) have been performed. A rapid resolution Zorbax Eclipse XDB-C18 column (4.6mm×50mm, 1.8μm particle size) has been employed and eighteen phenolic compounds belonging to different families have been identified and quantified spending a total time of 26 and 13min with UV–visible and MS detection, respectively. Response surface methodology has been applied by means of a central composite design for the optimization of the variables affecting the extraction procedure searching for the best recovery. The validation of the methods was performed through the establishment of the external standard calibration curves and the analytical figures of merit. Limits of detection ranging from 10 to 400ngmL−1 and 1 to 200ngmL−1 were achieved using UV–visible and MS detection, respectively. The extraction of phenolic compounds from virgin olive oil was performed in a simple and rapid way by RP-DLLME with ethanol:water 60:40 (v/v) as extracting solvent and 1,4-dioxane as disperser solvent. The quantification of the phenolic compounds in virgin olive oils from different olive varieties was carried out by means of the standard addition method and, finally the procedure for the sample treatment was validated using the well established solid phase extraction procedure with Diol cartridges.